Client-side fetch queries

[Janpot]

Attempt at adding a browserside mode to fetch queries:

Screen.Recording.2022-10-31.at.13.42.01.mov

Drawbacks of this method

• There is no way to get more diagnostics on failed fetches than "Failed to fetch". No way to find out whether it's because of CORs, or because of a firewall, or because of a DNS not resolving,...
• We can't supply the same information in the network tab as we can for serverside fetches. Currently it shows url, and some of the response headers. It can't show:
  • cookies
  • request headers
  • body sizes
  • timings
  • HTTP version
  • IP addresses

This only adds the mode, it doesn't yet update how the demo handles fetch requests

[render]

Your Render PR Server URL is https://toolpad-pr-1252.onrender.com.

Follow its progress at https://dashboard.render.com/web/srv-cdfs4ben6mpnq5hqcs5g.